ML20238B011
| ML20238B011 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 08/25/1987 |
| From: | Diederich G COMMONWEALTH EDISON CO. |
| To: | Davis A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 2821R, NUDOCS 8709010030 | |
| Download: ML20238B011 (2) | |
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@ Telephone 815/357-0761 Commonwealth i'diton LaSalle County Nuc lar Station RuralRoute #1,802220 Marseilles, Illinois 61341 PMOMTY[0M19 pg*
y Np-M L.y g2 August 25, 1987 Mr. A. Bert Davis Region III Administrator U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137
Dear Sir:
This special report is being submitted in accordance with LaSalle Unit 2 Operating License NPF-18, Appendix A, Technical Specification 4.8.1.1.3 and Regulatory Guide 1.108.
On July 27, 1987, at 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br />, with Unit 1 in Cold Shutdown and Unit 2 in Run at 98% power, the "0" Diesel Generator (D/G) output breaker to Engineered Safety Feature (ESP) bus 241Y failed to close on demand during its required monthly operability surveillance. The Nuclear Station Operator (Licensed Reactor Operator) performing the surveillance attempted two (2) additional times to close the breaker without success.
The operator had verified that the phase meter and Diesel Generator output voltage were correctly aligned for synchronization to the power grid during all three attempts.
The Unit 1 portions (the "0" D/G is a swing Diesel that can supply power to either 141Y or 241Y, 4.16KV buses) of the surveillance were completed without incident.
The "0" Diesel Generator was then declared inoperable with respect to Unit 2.
Initial troubleshooting efforts on the breaker close circuitry failed to produce the cause of the problem. However, it was discovered that the "0" D/G output breaker would close onto bus 241Y when the synchroscope meter indicated approximately 11:57 o' clock, but not at 12:00 o' clock.
Breaker closure is normally attempted at 12:00 o' clock per the synchroscope meter and all previous failed attempts at closure were attempted at 12:00 o' clock. Output breaker closure was attempted five (5) additional times at 11:57 o' clock to establish repeatability and all attempts were successful.
In addition, breaker closure was attempted five (d) times at 12:00 o' clock and all attempts were unsuccessful. The Unit 2 portions of the "0" D/G operability surveillance were then successfully completed and the "0" D/G declared operable at 2130 hours0.0247 days <br />0.592 hours <br />0.00352 weeks <br />8.10465e-4 months <br /> on July 27, 1987.
Y'Qh 8709010030 870825 PDR ADDCK 05000374 S
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Page 2 Output breaker closure is supervised by a synchrocheck relay which only allows i
breaker closure when the running and incoming phase voltages and frequency are j
within a certain design tolerance. Further investigation of the synchroscope
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revealed that it was out of calibration, and, closure attempts at 12:00 o' clock were actually being blocked by the synchrocheck relay. The sync!*roscope was replaced and the "0" D/G successfully tested.
1 Since the cause of this event was a malfunction of the Diesel Generator synchronizing circuitry, this event is not a valid test failure as defined by j
The LaSalle Unit 2 Diesel Generators have had one valid test failure in the last 100 starts and therefore the current testing l
frequency is once every 31 days.
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Diederich Station Manager LaSalle County Station GJD/HTV/mwh xc: Nuclear Licensing Administrator U.S. NRC Document Control Desk NRC Resident Inspector
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DOCUMENT ID 2821r/
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